Thread: Time Dialation Question View Single Post
P: 55
 Quote by JesseM Time dilation is based on what would be read by clocks moving along with each observer--in this case, the earth-twin's clock will say that 3.944 years have passed when they reunite, while the travelling twin's clock will say 1 year has passed. The two twins don't disagree about what the other twin's clock reads--the travelling twin agrees that 3.944 years have passed on the earth-twin's clock, and the earth-twin agrees that 1 year has passed on the travelling twin's clock. The earth going around the sun is just like another type of "clock" that stays at rest relative to the earth-twin, so of course everyone agrees it elapses 3.944 years as well. If the travelling twin carried a copy of the earth and sun along with him on the trip, then the duplicate earth would have only completed 1 orbit when the two twins reunited, and both twins would agree that this was true.
JesseM, my understanding of your words above is: if both twins departed at the age of n, when they united both twins agreed they were both (n + 3.944) years old, the same age according to the clock kept by the earth twin. On the other hand, according to the clock kept by the traveled twin, both agreed that both were (n + 1) years old, the same age. That is to say, whichever way we looked at it, there is no differential aging, no time dilation.